The present disclosure is directed to pipe testing apparatus and more particularly a system that is portable. It is the type of device which is intended to be hauled to a field location for the purpose of hydrostatic pressure testing of pipe. The term pipe as used herein refers to the tubular member without fittings on the end. The fittings are ordinarily called couplings. A joint is a pipe with an end located coupling. This apparatus is particularly useful for testing oilfield goods including tubing, drill pipe, and casing. The present apparatus, moreover, is directed to a portable test system which can be truck hauled by means of a tractor so that the present invention is constructed to accommodate a joint of pipe of standard length.
Ordinarily, a joint of pipe used in the oilfield is about 30 feet in length. That is, the hollow tube is manufactured to that length, and fittings or couplings are attached to the ends. Typically, the drill pipe length will be in the range of about 30-32 feet. Some casing is as long as 45 feet. Typically, a coupling is normally threaded to the pipe so that testing of the joint also involves testing of the threaded joint between the pipe and the coupling on the end. Some clearance must be obtained so that the joint can be engaged at both ends. One end will be described as the pin end and the other will be the box end, referring to whether the threads are on the exterior or interior. The box end is normally assembled by connecting a coupling on one end of the pipe to thereby present internal threads, hence forming a box end. Because there are variations from joint to joint in length and because joints having damaged threads can simply be trimmed and rethreaded, yielding a joint of perhaps 28 or 29 feet in length, the pipe testing apparatus must accommodate a length typically about 30 feet plus or minus about two feet. Some casing is up to 45 feet in length. This length, therefore, prescribes the approximate length of equipment necessary for testing purposes and taking into account end located equipment, the portable pipe testing apparatus is in the range of about 40 or even 45 feet in length. Assuming a 45 foot long structure, and further assuming a suitable trailer hitch or tongue mechanism for connection with a tractor, one approaches approximately 60 feet in length for a tractor pulled structure of this length. The present apparatus is, however, a portable pipe testing system which is folded in the middle to thereby shorten the length of the structure and to make it more readily portable without approaching 60 foot in length. Rather, the folded trailer is in the area of about 24 to 26 feet in length and can be attached to mid sized tractors in view of the fact that it is not exceedingly heavy and thus defined a truly portable pipe testing apparatus. Indeed, the length (when folded) is only about 35 feet for a system sufficiently long enough to test casing as long as 45 feet.
Attempts have been made heretofore to provide pipe testing systems. One such device is U.S. Pat. No. 4,067,228 showing a type of heavy rail system where a pipe is supported on wheeled carriers. It includes something similar to a spindle found in a metal lathe to rotate the pipe. A more recent patent is U.S. Pat. No. 4,571,986 which is directed to a pneumatic pipe leak tester apparatus. U.S. Pat. No. 4,470,295 is a structure which is mounted on a goose neck trailer showing various aspects of the pipe handling system. Recent U.S. Pat. No. 4,458,522 shows a set of parallel frame members which support spaced end located structures for testing a pipe, the end located structures being mounted on the frame members extending the length of the system. It uses threaded tension rods on both sides to maintain a tension-compression balance between the support structure and the pipe. A type of pipe gripping mechanism useful in such pipe systems for hydrostatic testing is described by U.S. Pat. No. 4,127,026. U.S. Pat. No. 3,710,628 is a trailer mounted pipe testing apparatus further disclosing an elongate main frame. The pipe testing apparatus of the present disclosure sets forth a type of portable folding trailer having a set of elongate lengthwise stringers and further including means for accommodating variations in pipe length so that hydrostatic testing can occur.
One feature of the present testing apparatus is the ability of the system to test a threaded joint. That is, it is able to engage the pin end without galling the threads on engagement. Rather, the joint ends are engaged by a surrounding resilient member confined within a sleeve which is positioned internally the end, and which is operated to swell against the joint, thereby forming a leakproof connection. This leakproof connection assists in sealing without actually using the threads. That is, the joint end is engaged by the resilient member but it is not threaded to the threads in the fashion of a threaded meet.
The type connection is also made at the opposite end which is the box end. There, the pipe terminates in a coupling which has a large surrounding exterior wall and engagement to the box end is accomplished by a surrounding resilient ring. On applying the proper squeeze to the resilient material, a leakproof connection is achieved.
The present test apparatus contemplates positive engagement with both ends simultaneously. While resilient members are applied, the joint is not loaded with an axial compressive loading. Rather, it is gripped at both ends but no loading is applied and hence, no distortion occurs. That is, the loading procedure holds the joint in position, engages both ends of the joint, but the position which is held does not involve excessive axial loading. In other words, axial loading is substantially reduced, and the joint is held in location for the test subject to only modest axial loading.
The present apparatus is constructed so that it will hinge in the middle to permit its removal to another location. The joint after testing can be kicked away and further processed. The test equipment, after its use, can thereafter be moved to another location by simply folding the lengthwise framework which is constructed with a pivot hinge, and structural integrity is thereby obtained in or throughout the structure of interest.
Structural integrity involves support of joint during testing. The joint is routinely filled with water and pressure applied to the water and half for an interval. It is not uncommon to apply pressures as high as 10,000 psi or greater. When pressures of this amplitude are applied, the loading along the length of the support structure for testing the joint is quite large. As an example, a joint have a nominal ID of 7.5 inches hydrostatically tested to 10,000 psi requires a reaction force of over 440,000 pounds to hold a test plug internally in the joint against the hydrostatic pressure maintained in the joint. This very substantial loading has to be carried by lengthwise stringers used in forming the apparatus.
The stringers which comprise the elongate trailer of this disclosure are deployed typically in a rectangular framework, there being two above and two below the joint. This defines left and right open sides so that the joint can be delivered into the test apparatus and removed after testing. The left and right slots typically enable adjacent joint racks to be positioned for transfer of the joint onto and away from the structure. Thus, one adjacent joint rack is the inbound rack and the other adjacent joint rack receives the tested joint.
This arrangement utilizing a surrounding framework adjacent to the joint during tests in conjunction with adjacent left and right joint racks provides a safety mechanism. It is possible, through no fault of the present apparatus, that a particular joint will catastrophically fail, thereby rupture, and perhaps explode, throwing large pieces of metal. The metal can not be thrown downwardly because it is blocked. Also, it can not be thrown upwardly because the stringers defining the length of the structure pass overhead and are connected with a suitable lattice work for structural reinforcing. As a consequence, safety is enhanced by reducing the window through which the joint might throw fragments during or as a result of a catastrophic metal failure. This confinement of the joint is beneficial in reducing the risk to operating personnel. Just as importantly, the joint is confined against lengthwise expansion, is held in resilient plugging mechanisms, and is therefore constrained by end located wheeled carriages supported on the stringers. The carriages are equipped with spindle type mechanisms which extend and thereby support the end located gripping mechanisms for alignment with the joint. Moreover, they move into and out of engagement with the joint without placing axial loading on the joint. The joint inevitably must be stressed when it is hydrostatically pressure tested. It is desirable to stress the joint and particularly the response of the joint to hydrostatic pressure without adding axial loads to the joint. This is accomplished by aligning and then moving end located carriages with the joint.
In summary, the present apparatus comprises an elongate framework assembled from parallel stringers, having carriage wheels under one end and having a jack under the opposite end to enable the stringer defined structure to be properly leveled. When it is installed, it is preferably tilted so that bubbles in the water filling the joint run to one end. The stringers are constructed with a hinge in the middle so that the long structure is folded in half and is more easily hauled on the highway. Another important feature relating to this is the incorporation of a trailer hitch whereby the structure, after folding, is then able to be hauled by trailer. A bogy is inserted under the folded structure, thereby serving as a set of front wheels for the towed trailer. The trailer weight can be carried on the hitch and the bogy omitted if desired.
With the foregoing background in mind, the present apparatus is summarized as a system which engages a joint with coupling, wherein the engagement prevents leakage while testing is undertaken. The testing process involves making a seal against the pipe end with a concentric rubber donut appropriately squeezed to provide sealing. Positioning of the rubber donut is assured by a concentric metal sleeve moreover, hydraulically actuated cylinders squeeze the donut to thereby swell the donut, the distortion in the resilient member assuring the seal. The device engages the joint at both ends and then releases, thereafter permitting testing of another joint.